This invention relates to the fields of firearms and ammunition and provisions for modifying automatic firearms for training purposes. In particular, it relates to automatic gas-operated weapons adapted to fire reduced-energy training ammunition in a blow-back mode and to said training ammunition.
In military and police firearms applications almost all of the ammunition consumed is used in training. For some training purposes, however, normal ammunition is not adequate. An alternative type of known training ammunition, represented by U.S. Pat. No. 5,359,937 (adopted herein by reference), fires a low-mass projectile relying on a special, reduced-energy cartridge designed to provide cycling of suitably-modified, recoil-operated or gas-operated automatic and semi-automatic weapons.
An advantage of the low-energy training ammunition is that it has a shorter range and lower penetration capacity than standard ammunition. This permits use of smaller, less-secure firing ranges as training facilities. If standard ammunition were accidentally employed in these facilities, unexpected dangers would arise from the increased striking power and range of standard ammunition.
Said training ammunition, in combination with certain modifications to the weapon, allows normal recoil and cartridge case ejection through a pure blow-back action. Such a system, when firing appropriate marking cartridges, makes for effective close-range, force-on-force training. This system enhances the realism and training value of interactive scenario tactical training because it allows trainees to use their service weapons in a representative manner in exercises simulating, for example, counter-terrorism, close quarters combat, trench clearing, fighting in wooded areas, urban fighting, and protection of dignitaries.
Modifications required to permit cycling of 9 mm automatic or semi-automatic weapons while firing low-energy ammunition, for example, generally include replacing or modifying the barrel and sometimes replacing or adding one or two other components, depending on the weapon involved. These modifications also serve to increase safety because the caliber of the substitute training barrel may be smaller than the diameter of the projectiles in standard 9 mm ammunition. If an attempt is made to chamber a standard cartridge in such a training-adapted or converted firearm, the barrel will not normally admit entry of the standard projectile. This ensures that such converted weapons cannot fire standard, live ammunition.
Firearms of other calibers, such as caliber .45 for pistols and 5.56 mm for automatic rifles, may also be converted to fire the same reduced-energy training ammunition using similar training barrels as described above for converted 9 mm pistols.
When firing standard ammunition, with its abundant associated energy, it is necessary in many weapons to lock the barrel to the slide (for pistols) or to the bolt carrier assembly (for gas-operated rifles) during the beginning of their rearward motion for a period long enough for the projectile to exit the barrel muzzle while the breech is still closed. This allows the chamber pressure to drop before the breech opens to extract and eject the spent cartridge case. A locking mechanism couples the barrel to the slide or bolt carrier assembly for the first portion of the recoil, and then releases said slide or bolt carrier assembly, usually with the aid of a cam. Upon unlocking, the slide or bolt carrier assembly continues its rearward travel until, after the spent cartridge case has been ejected, it returns under the influence of the recoil spring to receive and chamber the next round from the magazine en route to its in-battery position.
In a training system it is necessary to omit this barrel locking mechanism and, by so doing, the recoil action becomes pure blow-back of the slide or bolt carrier assembly only. This must be done because there is not enough energy in low-energy training cartridges to precipitate sufficient recoil to unlock the barrel from the slide or bolt carrier assembly in their standard configurations.
As implied above, 5.56 mm automatic weapons, as typified by the family of gas-operated M16A2 rifles and carbines made by the 1991 Colt""s Manufacturing Company Inc., can be modified to fire 9 mm reduced-energy training ammunition as represented by U.S. Pat. No. 5,359,937. This may be done by changing the barrel fitted to the upper receiver assembly as well as altering the bolt in the bolt carrier assembly to remove the locking mechanism. While such a design ensures the exclusion of live service ammunition from being fired from a converted weapon, it is costly to implement and awkward for the user due to the excessive number of weapon components involved.
An alternative approach is to modify only the bolt carrier assembly, leaving untouched the barrel, upper receiver assembly and the lower receiver buttstock assembly. In this way, the weapon can be rapidly converted to fire said reduced-energy training ammunition, by simply exchanging the service bolt carrier assembly for a training bolt carrier assembly. It is, therefore, an objective of this invention to provide a quick and easy conversion of this class of weapons from its service operating configuration to a training operating configuration without modification to the barrel, the upper receiver assembly or said lower receiver buttstock assembly.
This means, however, that live service ammunition would not be excluded from chambering in the standard 5.56 mm barrel, which is connected to the upper receiver assembly. Thus, for this approach to be acceptable from a safety point of view, it is essential that a mechanism be included in the design of the training bolt carrier assembly, in combination with the said reduced-energy cartridge, that will positively prevent the firing of live service ammunition from a 5.56 mm weapon converted to fire said training cartridges.
It is, therefore, another objective of this invention to provide a conversion system for the class of gas-operated weapons typified by the family of M16A2 rifles and carbines that will permit the safe firing of training ammunition while positively excluding the firing of a live round of service ammunition should one be inadvertently chambered during training exercises or practice scenarios.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principal of the invention and the manner of its implementation. The invention in its broadest and more specific forms will be further described, and defined, in each of the individual claims which conclude this specification.
This invention is preferably directed to gas-operated automatic weapons, as typified by the Colt M16A2 family of rifles and carbines, converted to fire reduced-energy training ammunition as represented by U.S. Pat. No. 5,359,937. The invention is also applicable to all cases where a training bolt carrier assembly having a recessed end on the bolt is substituted in place of a standard service bolt carrier assembly without further modification to the weapon.
According to one aspect of the invention a training bolt is provided for a converted firearm wherein the training bolt has a recess through which the firing pin advances. The recess is dimensioned to exclude the head end of a standard cartridge, locating the head end beyond reach of the firing pin. The recess is, however, dimensioned to receive the head end of training ammunition that will fit into the recess, locating the primer of the training round within reach of the firing pin.
The selective shaping of the recess and training round may be effected by reducing the diameter of the recess to exclude entry by the head end of a standard round while receiving the head end of a training round which is of reduced diameter. Alternately, the recess may have a protrusion in its bottom, seating end that excludes entry of the head end of a standard cartridge; while training cartridges may have a complementary recess formed within the head end that will interfit with the protrusion. Thus, the training round can be seated for firing, but a standard round will be excluded. Similarly, the rim of the training cartridge and the matching front end recess of the training bolt could be dimensioned to be of some shape other than circular.
In the conversion of an M-16 type firearm the standard pin, extractor and ejection pin may be retained. The new training bolt carrier assembly may omit the barrel locking feature present in the standard weapons by: (1) replacing the cam groove in the bolt carrier by a simple cylindrical hole through which a standard cam pin rigidly attaches the training bolt to the training bolt carrier; and (2) eliminating the gas port. Since the bolt locking lugs are, therefore, unable to rotate and engage the barrel extension in the in-battery or closed position, the converted weapon operates in a pure blow-back mode when firing said reduced-energy training ammunition. Further, because there is no locking action, retention of the bolt locking lugs is optional.
The round-engaging end of the bolt of an M-16 type firearm has a recess. Normally, the rim at the head end of a standard round of service ammunition fits snugly into this recess and is gripped there by the extractor, which fits over the rim and settles into the extraction groove. In this position, the primer face at the head end of the cartridge is flush against the flat bottom of the bolt recess, adjacent the tip of the retracted firing pin located therein. When the trigger is pulled, the firing pin thrusts forward into the recess region and strikes the primer, thereby firing the weapon.
With a training round having a reduced head-end rim diameter, however, the recess in the front end of the training bolt is not large enough to accept a standard round of 5.56 mm service ammunition. Therefore, since the depth of the recess is considerably greater than the stroke of the firing pin, there is no contact between the tip of the firing pin and the primer after the firing pin has been activated and thrust into the recess. As a result, the round does not fire and the modified weapon will not expose users to the risk that a standard round may be inadvertently discharged.
According to a further aspect of the invention, the training bolt carrier assembly is free to recoil as part of a blow-back cycling operation for reloading the weapon. Blow-back operation may be achieved by employing a telescopically lengthening cartridge case as described in U.S. Pat. Nos. 5,359,937 and 5,492,063. The external form of the reduced-energy training ammunition as represented by U.S. Pat. No. 5,359,937, may be produced in a form that is identical to that of the standard 5.56 mm cartridge case except for the diameter of the rim at the head of the case. This diameter may, however, be reduced so that it will fit snugly into the reduced diameter of the training bolt. Thus, such training ammunition will seat properly within the recess formed in the training bolt, with its head end flush against he bottom of the recess, adjacent and in the path of the retracted tip of the firing pin. In this configuration, the firing pin will strike the primer and fire the weapon in the normal way when said firing pin is activated. The telescopic lengthening of the cartridge will effect the blow-back cycling of the weapon.
The foregoing summarizes the principal features of the invention and some of its optional aspects. The invention may be further understood by the description of the preferred embodiments, in conjunction with the drawings, which now follow.